The anterior cruciate ligament (ACL) spans the knee, joining the femur bone of the upper leg and the tibia bone of the lower leg. The ACL enables the knee to bend so that the leg below the knee can move in relation to the leg above the knee. Injuries to the ACL are very common, especially among athletes.
When the ACL is torn it can not be directly repaired with a suture, but must instead be reconstructed using grafted donor tissue which is placed across the knee in the same position and orientation as the ACL it replaces through two tunnels, one drilled in the tibia and the other in femur. To ensure proper range of motion of the reconstructed knee, the tunnels should be collinear. At present, a conventional tibial aiming device, shown in FIG. 1 and described in more detail below, is used to assist a surgeon in determining the proper angle at which the tunnels should be drilled through reference points selected on the tibia and femur, respectively, so that the tunnels are collinear.
Conventional tibial aiming devices suffer from a significant drawback. Specifically, they rely upon the eyes of a surgeon to determine the angle at which the tunnels should be drilled with respect to the aforementioned reference points. However, relying upon one's eyesight to estimate this angle often results in tunnels that are not collinearly formed and thus an improperly reconstructed ACL.